Thick film circuits may be formed using an additive process in which successive layers of materials are disposed on an electrically insulating substrate. Thick film conductive elements can be formed, for example, by screen printing a thick film conductive ink that is formulated with a powdered base metal onto a non-conductive substrate. The thick film conductive ink may then be dried and fired to sinter or fuse the powdered base metal and other remaining constituents to the substrate. The substrate may be processed (e.g., scribing, profiling, drilling, dicing, etc.) either before, during, or after an additive process used to form a thick film circuit.
The conductive inks may be used to form electrodes, resistors, terminals, and other features of the circuit. The function of the circuit may be determined by a design printed onto the substrate and a combination of features included on the circuit. The circuit may be further designed with termination pads for attaching semiconductor chips, connector leads, capacitors, and the like.
Thick film circuits have conventionally been fabricated using precious metals as the primary conductive element. The high cost of precious metals contributes significantly to the cost of creating thick film and hybrid circuits using thick film production techniques. Although base metals have a lower cost, a variety of factors has previously presented challenges to utilizing such metals in thick film circuits, specifically multilevel circuits.
The inventors of the present disclosure have recognized that potential benefits may be achieved by using base metals in thick film circuits that have traditionally been formed using precious metals.